Method and system for forming a self-sealing volume with an aqueous polyurethane dispersion layer

ABSTRACT

A fabric coated or impregnated with an elastomeric material may include a polyurethane dispersion layer combined with a sealant. The fabric may be applied in such a fashion so as to enable the elimination of solvent or fluid that is associated with the elastomer. The polyurethane dispersion layer generally comprises an elastomeric material dispersed or dissolved in a liquid medium, such as, but not limited to, water. At the same time, the integrity of the elastomeric composite which is formed from the dispersion and sealant layers may be maintained in order to minimize the presence of air voids and pockets. It has thus been realized that in doing so the performance of the self-sealing volume is dramatically improved. This method of construction usually may be accomplished without significantly adding to the weight or thickness of the volume and without affecting the outer dimension of the self-sealing volume.

DESCRIPTION OF THE RELATED ART

The present invention is related generally to the field of containersfor materials, and more specifically related to the field ofself-sealing fuel tanks. These tanks are frequently preferred inapplications where fuel fire and explosion risks are high, as inmilitary, armored and racing vehicles.

Self-sealing fuel tanks currently exist in the conventional art. Oneproblem with these conventional self-sealing fuel tanks is that they aremanufactured using labor intensive hand layup processes that requirelong cure times. Large numbers of self-sealing fuel tanks thus cannot bemanufactured over a reasonable time period.

In addition, these conventional manufacturing techniques do not allowfor precise control of the outer dimensions of self-sealing fuel tank, aproblem where tight fits are required and maximum fuel capacity isdesired. A closed molding process would allow for precise control of theouter dimensions of self-sealing fuel tank.

Alternative materials of manufacture can be used that do not require thelabor intensity and long cure times but these materials typically resultin composite that lacks flexibility, has increased weight or preventsthe use of a closed molding process. Solvated elastomeric materials andelastomeric dispersions for example, while beneficial in that they arelow viscosity and can therefore be easily applied, typically cannot beused because a closed mold inhibits the escape of high vapor pressurefluids such as water and solvent. It usually is not possible to controlthe evaporation of certain fluids of these materials during a closedmolding process.

Accordingly, there is a need in the art for a method in formingself-sealing volumes that enables the use of elastomeric dispersions andsolvated elastomers in a closed molding process where it is possible tocontrol the evaporation of fluids and precisely control the fuel tankouter dimensions.

BRIEF SUMMARY OF THE INVENTION

It has been discovered that a fabric coated or impregnated with anelastomeric material (referred to later as an elastomeric material andfabric), that may include a polyurethane dispersion layer combined witha sealant may be applied in such a fashion so as to enable theelimination of solvent or fluid that is associated with the elastomer.The polyurethane dispersion layer generally comprises an elastomericmaterial dispersed or dissolved in a liquid medium, such as, but notlimited to, water. At the same time, the integrity of the elastomericcomposite which is formed from the dispersion and sealant layers may bemaintained in order to minimize the presence of air voids and pockets.It has thus been realized that in doing so the performance of theself-sealing volume is dramatically improved. This method ofconstruction usually may be accomplished without significantly adding tothe weight or thickness of the volume and without affecting the outerdimension of the self-sealing volume.

Thus, a method for forming a self-sealing volume is described. Thesystem includes an elastomeric composite structure comprisingpolyurethane dispersion layer and at least one layer of an elastomerimpregnated fabric. The structure further may include at least one layerof a fabric, and at least one sealing layer. A fuel impermeable innerliner may be positioned in an inner region relative to the other layers.

The fabric may comprise fibers made from nylon, polyester, polyethyleneand polypropylene materials. The fabric and self-sealing layers arepositioned relative to each other so as to create a path for solvent orwater to escape when the volume is heated and pressurized to consolidatelayers.

The at least one sealing layer may comprise at least one of anunvulcanized or partially vulcanized natural rubber (NR), a polyisoprene(IR), a styrene butadiene (SBR), or a blend of these materials. In otherexemplary embodiments, the sealing layer may comprise polyurethane. Inother exemplary embodiments, the sealing layer may comprise fullyvulcanized (>1% sulfur) rubber. Other alternative materials for thesealing layer may include, but are not limited to, aliphaticpolyurethanes. These materials can also be manufactured to include acalendered scrim material.

Another inventive aspect of the method and system is that the preformrelease layer is inflated during curing of the elastomeric materiallayer. With this inflation of the preform release layer, the elastomericcomposite layer conforms to the exact dimensions of the mold that holdsthe preform and the elastomeric composite sandwiched there between. Atthe same time solvent or water and air are driven out of the compositestructure. This process yields a dimensionally correct/precisely builtself-sealing volume.

BRIEF DESCRIPTION OF THE DRAWINGS

In the Figures, like reference numerals refer to like parts throughoutthe various views unless otherwise indicated. For reference numeralswith letter character designations such as “102A” or “102B”, the lettercharacter designations may differentiate two like parts or elementspresent in the same figure. Letter character designations for referencenumerals may be omitted when it is intended that a reference numeral toencompass all parts having the same reference numeral in all Figures.

FIG. 1A is a cross-sectional view of a self-sealing volume in the formof a fuel tank according to one exemplary embodiment.

FIG. 1B is a cross-sectional view of a portion of a wall of aself-sealing volume according to one exemplary embodiment.

FIG. 2A is a cross-sectional view of an entire wall for a self-sealingvolume according to the exemplary embodiment of FIG. 1.

FIG. 2B is a cross-sectional view of the wall of FIG. 2A in which aprojectile has begun to penetrate the wall entering from outside of theself-sealing volume towards the inside of the volume containing a fluid,such as fuel.

FIG. 2C is a cross-sectional view of the wall of FIG. 2B in which theprojectile has continued to penetrate the wall from the outside of theself-sealing volume towards the inside of the volume containing a fluid,such as fuel.

FIG. 2D is a cross-sectional view of the wall of FIG. 2C in which theprojectile has continued to penetrate the wall from outside of theself-sealing volume towards the inside of the volume containing a fluid,such as fuel.

FIG. 2E is a cross-sectional view of the wall of FIG. 2D in which theprojectile has completely penetrated the wall and has entered into thevolume containing the fluid, such as fuel, and allowing the fluid toreact with the sealing layer.

FIG. 2F is a cross-sectional view of the wall of FIG. 2E in which thefluid continues to react with the sealing layer causing the sealinglayer to further expand into the close the volume containing the fluid.

FIG. 3A is a diagram illustrating fibers receiving a polyurethanecoating.

FIG. 3B is a diagram illustrating a fabric receiving a polyurethanecoating.

FIG. 4A is a cross-sectional view of a preform, a release layer, and aliner.

FIG. 4B is a cross-sectional view of an intermediate product thatcomprises the wall layers of FIG. 1 in addition to the preform, therelease layer, and liner of FIG. 4A.

FIG. 4C is a diagram illustrating how the intermediate product of FIG.4B is positioned within a mold according to one exemplary embodiment.

FIG. 4D is a diagram illustrating a cured intermediate product after theintermediate product is removed from the mold of FIG. 4C.

FIG. 4E is a diagram illustrating the formation of the completed productof FIGS. 2A-2F by removal of the preform and release layer.

FIG. 4F1 is a cross-sectional view of a self-sealing volume in the formof a fuel tank illustrating the individual composite layers along withpaths of air escape according to one exemplary embodiment.

FIG. 4F2 is a cross-sectional view of an elastomeric material and fabricthat is depicted in FIG. 4F1.

FIG. 4G is a cross-sectional view of a corner of a self-sealing volumeillustrating an alternative layup pattern where one or more structuralfabric plies are located on one side of the sealant layer.

FIG. 4H is a cross-sectional view of a corner of a self-sealing volumeillustrating an alternative layup pattern where three or more structuralfabric plies are separated by the sealant layer.

FIG. 4I is a side view of a corner of a self-sealing volume illustratingan alternative lay-up pattern where the sealant material has beenperforated with holes. The sealant is subsequently covered with fabricand the holes are covered with sealant patches that are larger than theoriginal holes. The holes can be any shape.

FIG. 4J1 is a side view of an intermediate self-sealing volumeillustrating an inner layer of the elastomeric material and fabriclayer.

FIG. 4J2 is a side view of an intermediate self-sealing volumeillustrating the sealant applied with a gap over the elastomericmaterial and fabric of FIG. 4J1.

FIG. 4J3 is a side view of an intermediate self-sealing volumeillustrating a breather fabric applied over the gap illustrated in FIG.4J2.

FIG. 4J4 is a side view of an intermediate self-sealing volumeillustrating a sealant patch applied over the gap and breather fabric ofFIG. 4J3.

FIG. 4J5 is a side view of an intermediate self-sealing volumeillustrating an outer layer of the elastomeric material and fabricapplied over the sealant patch and sealant of FIG. 4J4.

FIG. 4K1 is a side view of an intermediate self-sealing volumeillustrating an inner layer of the elastomeric material and fabriclayer.

FIG. 4K2 is a side view of an intermediate self-sealing volumeillustrating the sealant applied with a gap over the elastomericmaterial and fabric of FIG. 4K1.

FIG. 4K3 is a side view of an intermediate self-sealing volumeillustrating a calendared sealant patch applied over the gap and sealantof FIG. 4K2.

FIG. 4K4 is a side view of an intermediate self-sealing volumeillustrating an outer layer of the elastomeric material and fabricapplied over the calendared sealant patch and sealant of FIG. 4K3.

FIG. 4K5 is a cross-sectional top, view of the calendared sealant patchembodiment of FIG. 4K4.

FIG. 4K6 is a front view of the calendared sealant patch of FIG. 4K3illustrated alone.

FIG. 4K7 is a side view of the calendared sealant patch illustrated inFIG. 4K6 illustrated alone.

FIG. 4L1 is a side view of an intermediate self-sealing volumeillustrating an inner layer of the elastomeric material and fabriclayer.

FIG. 4L2 is a side view of an intermediate self-sealing volumeillustrating the sealant applied with a gap over the elastomericmaterial and fabric of FIG. 4L1.

FIG. 4L3 is a side view of an intermediate self-sealing volumeillustrating a breather fabric strips applied over the gap illustratedin FIG. 4L2.

FIG. 4L4 is a side view of an intermediate self-sealing volumeillustrating a sealant patch applied over the gap and breather fabricstrips of FIG. 4L3.

FIG. 4L5 is a side view of an intermediate self-sealing volumeillustrating an outer layer of the elastomeric material and fabricapplied over the sealant patch and sealant of FIG. 4L4.

FIG. 5A is a flowchart illustrating a method for forming a self-sealingvolume according to an exemplary embodiment.

FIG. 5B is a continuation flowchart of FIG. 5A illustrating the methodfor forming a self-sealing volume according to an exemplary embodiment.

FIG. 5C is a continuation flowchart of FIG. 5B illustrating the methodfor forming a self-sealing volume according to an exemplary embodiment.

FIG. 6 a flowchart illustrating an optional routine or submethod forcreating a polyurethane elastomer according to an exemplary embodiment.

FIG. 7A1 is a cross-sectional view of a device for forming flexiblemolds according to an exemplary embodiment.

FIG. 7A2 is a cross-sectional view of the flexible molds formed from thedevice of FIG. 7A1 according to an exemplary embodiment.

FIG. 7A3 is a cross-sectional view of preform material positioned withinthe flexible molds of FIG. 7A2 according to an exemplary embodiment.

FIG. 7A4 is a cross-sectional view of the two halves of a gas-permeable,solid preform generated from the flexible molds of FIG. 7A3 according toan exemplary embodiment.

FIG. 7A5 is a cross-sectional view of the two halves of thegas-permeable, solid preform put together according to an exemplaryembodiment.

FIG. 7A6 is a cross-sectional view of the two halves of thegas-permeable, solid preform after apertures or holes have been createdwithin the preform according to an exemplary embodiment.

FIG. 7B1 is a cross-sectional view of a solid mold for forming agas-impermeable, hollow preform according to an exemplary embodiment.

FIG. 7B2 is a cross-sectional view of the solid mold of FIG. 7B1 with afixture attached to a side of the solid mold having an apertureaccording to an exemplary embodiment.

FIG. 7B3 is a cross-sectional view of the solid mold in which a liquidstate of the preform material is poured into the solid mold via thefixture according to an exemplary embodiment.

FIG. 7B4 is a cross-sectional view of the solid mold containing thepreform liquid material while the solid mold is being rotated accordingto an exemplary embodiment.

FIG. 7B5 is a cross-sectional view of the solid mold being opened aftercuring of the preform liquid material into an gas-impermeable, hollowpreform according to an exemplary embodiment.

FIG. 7B6 is a cross-sectional view of the gas-impermeable, hollowpreform after apertures or holes have been created within the preformaccording to an exemplary embodiment.

FIG. 7C illustrates a cross-sectional view of a device for formingflexible molds according to an exemplary embodiment.

FIG. 8 is a flowchart illustrating a routine or submethod for generatingthe solid preform of FIG. 7A according to an exemplary embodiment.

FIG. 9 is a flowchart illustrating a routine or submethod for generatingthe hollow preform of FIG. 7B according to an exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects.

FIG. 1A is a cross-sectional view of a self-sealing volume or wallsystem 200 in the form of a fuel tank according to an exemplaryembodiment. The wall system 200 comprises a wall 100 and a liner 202which will be described in more detail below. The wall system 200 maycontain a fluid 204, such as, but not limited to, a hydrocarbon fuel.The wall system 200 may further comprise a nut ring 509 containing anaccess port 405 which will be described below in connection with FIGS.4C-4E. The nut ring 509 is fitted/mates with the metal fixture 507 (FIG.7) as will be described below. The wall system 200 may comprise acomposite of elastomeric material and fabric as described in furtherdetail below. The composite of elastomeric material and fabric mayinclude a self-healing layer for sealing after ballistic penetration.

Referring now to FIG. 1B, this figure is a cross-sectional view of aportion of a wall 100 for forming the self-sealing volume or wall system200 (of FIG. 1A) according to one exemplary embodiment. The wall 100 maycomprise an elastomeric composite that includes a combination of layerssuch as, for example, a polyurethane dispersion layer 102, a fabric orfiber layer 104, and a sealant layer 106.

In the exemplary embodiment illustrated in FIG. 1B, the wall 100 maycomprise a fuel resistant outer liner 103, a first fabric or fiber layer104A, a second elastomeric material such as a polyurethane dispersionlayer 102B, a sealant layer 106, a third elastomeric material such as apolyurethane dispersion layer 102C, a second fabric were fiber layer104B, and a fourth elastomeric material such as a polyurethanedispersion layer 102D.

The fuel resistant outer liner 103 may comprise an aqueous anionicdispersion of a high molecular weight polyurethane, such as, but notlimited to, a molecular weight of about 335,000.00. This dispersioncomprises high molecular weight polyurethane dispersed or dissolved in aliquid medium, such as, but not limited to, water and is thencross-linked by incorporating a cross-linking polymer, such as a wasterdispersible polyisocyanate, an organofunctional silane, a polyaziridineor a polycarbodiimide, in the polyurethane dispersion.

The fuel resistant outer liner 103 may be applied by brushing,troweling, or spraying, or other ways as understood by one of ordinaryskill in the art. After the outer liner 103 has been sufficientlyapplied onto the fabric or fiber layer 104, then the coating is ready tobe activated and cured.

The polyurethane dispersion layers 102 may comprise an aqueous anionicdispersion of a high molecular weight polyurethane, such as, but notlimited to, a molecular weight of about 335,000.00. This means that thepolyurethane dispersion layer 102 generally comprises high molecularweight polyurethane dispersed or dissolved in a liquid medium, such as,but not limited to, water. The polyurethane dispersion layers 102 aredesigned to dry and become somewhat tacky at room temperature, which istypically about 25.0° C. as understood by one of ordinary skill in theart. Further heating will drive off any water, causing the elastomer tocoalesce and develop desired material properties for storing liquids,like fuels.

Other aqueous elastomeric dispersions may be used. Other aqueouselastomeric dispersions include, but are not limited to, Polychloroprene(Neoprene) latex, Styrene butadiene (SBR) latex, Acrylonitrile butadiene(NBR) latex, Chlorosulfonated polyethylene (Hypalon) latex, Ethylenepropylene diene monomer (EPDM) latex, and the like. Solvated elastomersmay also be used. Some solvated elastomers include, but are not limitedto Polychloroprene (Neoprene), Styrene butadiene (SBR), Acrylonitrilebutadiene (NBR), Chlorosulfonated polyethylene (Hypalon), Ethylenepropylene diene monomer (EPDM), Polyvinylidene fluoride (FKM),Polysulfide, Hydrogenated nitrile butyl rubber (HNBR), and the like.

A cross-linked elastomeric material may also be used in the dispersionlayers 102. Such a material can be made by incorporating a cross-linkingpolymer, such as a waster dispersible polyisocyanate, anorganofunctional silane, a polyaziridine or a polycarbodiimide, in thepolyurethane dispersion. A cross-linked elastomeric material willusually improve the compression set and minimize plastic deformation athigher temperatures. As understood by one of ordinary skill in the art,compression set is the tendency of elastomers to undergo permanentdeformation. It is the tendency of some elastomers to not recover in acompletely elastic manner. An addition of a crosslinking waterdispersible polyisocyanate such as described above may remedy thischaracteristic. This compression set property may be measured by ASTMD395. As understood by one of ordinary skill in the art plasticdeformation at higher temperatures is the tendency of elastomers topermanently deform from their original shape when heated above thesoftening or melting temperature. The addition of a crosslinking waterdispersible polyisocyanate such as described above may remedy thischaracteristic. The softening or melting temperature may be measured byASTM D3418-03.

The polyurethane dispersion layers 102 may be applied by brushing,troweling, swabbing, dipping or spraying, or other ways as understood byone of ordinary skill in the art. After the polyurethane dispersionlayer 102 has been sufficiently spread and incorporated into the fabricor fiber layer 104, then the elastomeric composite formed by layers 102and 104 is ready to be activated and cured.

Debulking may also be used during the layup process and can beaccomplished in a number of ways as understood by one of ordinary skillin the art. This debulking further consolidates the multiple layers toensure the final composite can be installed into the cure mold as wellas remove additional water or solvents which further decreases finalcure cycle times. A sufficient temperature for debulking is generallybetween about 25.0° C. to about 120.0° C., and preferably between about50.0° C. to about 100.0° C., and more preferably at about 83.0° C.

The polyurethane dispersion 102 is selected such that heat is requiredfor activation and cure. Heat can be supplied from a conventional oven,an autoclave, a microwave oven or from a press, or alternative ways asunderstood by one of ordinary skill in the art. Once the liquidpolyurethane dispersion layer 102 is applied onto the respectivecomposite layers of a wall portion, the entire uncured structure may beplaced into a three dimensional, dimensionally correct mold 400 (as willbe described below in connection with FIG. 4). Curing is effected byheating the mold 400 to a sufficient temperature and for a sufficienttime to cause the polyurethane dispersion to eliminate remaining waterand to coalesce to form a solid polyurethane layer 102. A sufficienttemperature is generally between about 83.0° C. to about 176.0° C., andpreferably between about 100.0° C. to about 160.0° C., and morepreferably at about 149.0° C. However, other temperatures may be used asunderstood by one of ordinary skill in the art and are within the scopeof this disclosure. The time for coalescing is generally between about5.0 minutes to about 120.0 minutes (min), and preferably between about20.0 min to about 80.0 min, and more preferably for about 60.0 min.However, other times may be used as understood by one of ordinary skillin the art and are within the scope of this disclosure. As notedpreviously, the amount of pressure provided by the gaseous pressuresource 403 is generally between about 2.0 psi to about 80.0 psi, andpreferably between about 10.0 psi to about 40.0 psi, and more preferablyat about 20.0 psi. However, other pressures may be used as understood byone of ordinary skill in the art and are within the scope of thisdisclosure.

In addition to polyurethane dispersions that are used as the elastomericcomponent of the composite, other elastomeric materials may also beused. Such elastomeric materials may include but are not limited tostyrene butadiene rubber dispersions, nitrile butyl rubber dispersions,polychloroprene dispersions, polyurethane dispersions, polyureadispersions, silicone dispersions, solvated polyureas, solvatedpolyurethanes, solvated nitrile butyl rubber, solvated polychloroprene,solvated polyvinylidene fluoride, silicones, polysulfides, polyurethaneureas, epoxy, polyester and other materials that can be applied at a lowviscosity and then cured to form an intractable but flexible elastomer.

The fabric or fiber layer 104 may comprise polyamide, aramid, polyester,polypropylene or polyethylene fibers or coated fabrics of the samematerials. The coating on the fibers or fabrics in layer 104 maycomprise solvated or aliphatic polyurethane that is applied during thefiber or fabric manufacturing process. As understood by one of ordinaryskill in the art, aliphatic is a general class of polyurethanes(excluding aromatic) which is typically easier to solvate than aromaticpolyurethanes. The coating may also comprise a resorcinol formaldehyde(RFL) or an isocyanate. Further details of this coating for the fibersor fabric layer 104 are described below in connection with FIGS. 3A-3B

As understood by one of ordinary skill in the art, polyamide is a classthat includes NYLON and anisotropic aromatic polyamide (such asKEVLAR™). As understood by one of ordinary skill in the art, polyesteris a class that includes polyethylene terephthalate and anisotropicaromatic polyesters. The fabric may comprise at least one of NYLON 6,NYLON 66, polyester, an anisotropic aromatic polyamide, or ananisotropic aromatic polyester from about 5.0 ounces per square yard(“oz/SY”) to about 30.0 oz/SY. It is possible to use other fibers andfabrics with the elastomeric material layer 102, but polyamide andpolyester fibers and fabrics are preferred due to their physicalperformance characteristics in ballistic and blast situations.

The sealant layer 106 typically is sandwiched between two elastomericmaterial layers 102 and two or more fabric or fiber layers 104 forreinforcement. Typical materials suitable for use as the sealant layer106 may comprise unvulcanized, partially vulcanized and/or vulcanizednatural rubber (NR). Other materials that may be used includepolyisoprene (IR), styrene butadiene (SBR) and blends of SBR with NR orIR. In other exemplary embodiments, the sealant layer 106 may beunvulcanized. In other exemplary embodiments, the sealant layer 106 maycomprise fully vulcanized (>1.0% sulfur) rubber. Other alternativematerials for the sealant layer 106 may include, but are not limited to,aliphatic polyurethanes. The sealant layer 106 is illustrated in FIGS.1B and 2A-2F as a solid layer. The thickness of the sealant layer canrange from 0.015″ to about 0.25″, but preferably 0.12″. In alternateexemplary embodiments, the sealant layer 106 may comprise multiple solidsealant layers that enclose a scrim fabric as understood by one ofordinary skill in the art. The thickness of the individual solid sealantlayers that enclose the scrim fabric can range from 0.015 to about0.125″, but preferably 0.060″. Other sizes and dimensions for the scrimfabric may be employed without departing from the scope of thisdisclosure. For example, the scrim fabric may comprise a weight ofbetween about 2 oz to about 12 oz, but preferably about 7 oz. The scrimfabric may comprise polyimide, aramid, polyester, polypropylene orpolyethylene fibers or coated fabrics of the same materials and includewoven or non-woven materials.

While the thicknesses of each of the layers illustrated in FIG. 1 havebeen shown to be equivalent, one of ordinary skill in the art willrecognize that the actual thicknesses of each layer may vary and may beadjusted depending upon the level of protection desired for a particularvolume. Wall gauge design dimensions are usually driven by weightrestrictions, ballistic needs and overall flexibility requirements. Forexample, the finished product for the self-sealing wall portion 100typically has the following dimensions according to one illustrativeembodiment: a first fabric or fiber layer 104A having a thickness ofapproximately 0.5 to approximately 2.0 mm; a second elastomeric materiallayer 102B having a thickness of approximately 0.1 to approximately 1.0mm; a sealant layer 106 having a thickness of approximately 0.5 toapproximately 13.0 mm; a third elastomeric material layer 102C having athickness of approximately 0.1 to approximately 1.0 mm; a second fabricor fiber layer 104B having a thickness of approximately 0.5 toapproximately 2.0 mm; and a fourth elastomeric material layer 102Dhaving a thickness of approximately 0.1 to approximately 1.0 mm.

Referring now to FIG. 2A, this figure is a cross-sectional view of anentire wall or wall system 200 for a self-sealing volume according toone exemplary embodiment. The wall system 200 comprises all of thelayers of the wall 100 described above in connection with FIG. 1B, inaddition to a liner layer 202 and the fluid 204.

The liner layer 202 may comprise any elastomeric material that will havea greater resistance to hydrocarbon fuel 204 than the elastomericmaterial 102. Exemplary materials include, but are not limited to,nitrile rubber, polyurethane, polysulfide and polyvinylidene fluoride,polyurea, polyvinylalchohol (PVA), Hydrogenated Nitrile Butadiene Rubber(HNBR), Epichlorohydrin rubber (ECO), or any fuel resistant elastomer.An optional barrier layer, described below, may also be used andpositioned on the outside of the liner layer 202.

The fluid 204 may comprise a fuel, and particularly a hydrocarbon fuel204, such as gasoline, diesel-based fuels, biofuels, and ethanol fuelsused in military crafts such as airplanes, boats, helicopters, tanks,cars, jeeps, all-terrain-vehicles (ATVs), and other similar vehicles.The wall 100 provides a self-sealing barrier and protection for theliner layer 202 in order to contain the fluid 204 within the entire wallsystem 200.

FIG. 2B is a cross-sectional view of the wall system 200 of FIG. 2A inwhich a projectile 206 has begun to penetrate the wall system 200entering from outside of the self-sealing volume towards the inside ofthe volume containing a fluid 204, such as fuel. The projectile 206 maycomprise any type of object that is launched from a gun or ballisticsystem, such as a bullet or fragment, and/or fragments from highvelocity vehicle accidents. In the exemplary embodiment illustrated inFIG. 2B, the projectile 206 has already penetrated the first elastomericmaterial layer 102A and is starting to enter the first fabric or fiberlayer 104A.

FIG. 2C is a cross-sectional view of the wall system 200 of FIG. 2B inwhich the projectile 206 has continued to penetrate the wall system 200from the outside of the self-sealing volume towards the inside of thevolume containing a fluid 204, such as fuel. In this exemplaryembodiment, the projectile 206 has penetrated through the firstelastomeric material layer 102A, the first fabric or fiber layer 104A,the second elastomeric material layer 102B, the sealant layer 106, thethird elastomeric material layer 102C, the second fabric or fiber layer104B, and has started to enter the fourth elastomeric material layer102D.

FIG. 2D is a cross-sectional view of the wall system 200 of FIG. 2C inwhich the projectile 206 has continued to penetrate the wall system 200from outside of the self-sealing volume towards the inside of the volumecontaining a fluid 204, such as fuel. In this exemplary embodiment, theprojectile 206 has penetrated through all the layers of the wall system200 including the liner layer 202 and has entered the volume containingthe fluid 204 itself. Specifically, the projectile 206 has penetratedthrough all four layers of the elastomeric material layers 102, the twofiber or fabric layers 104, the single sealant layer 106, and the linerlayer 202.

FIG. 2E is a cross-sectional view of the wall system 200 of FIG. 2D inwhich the projectile has completely penetrated the wall system 200 andhas entered into the volume containing the fluid 204, such as fuel, thusallowing the fluid 204 to react with the sealant layer 106. In thisexemplary embodiment, the fluid 204 which may comprise a fuel such as ahydrocarbon fuel may interact with the sealant layer 106 which maycomprise unvulcanized or partially vulcanized natural rubber (NR). Othermaterials that may be used for the sealant layer 106, as describedabove, may include but are not limited to polyisoprene (IR), styrenebutadiene (SBR) or blends of SBR with NR or IR.

In this exemplary embodiment, the sealant layer 106 includes a firstportion 106A which has expanded into the cavity 210A formed by theprojectile 206. The sealant layer 106 is selected from materials thatare tacky in nature and which may have autoadhesion characteristics.Such materials may also swell around openings formed by projectiles thatpenetrate the materials. In other cases, it is believed that swelling ofthe sealant layer could occur due to a reaction between the sealant anda hydrocarbon liquids or any other type of liquid which may be stored inthe self-sealing volume.

The sealant materials are generally themselves hydrocarbon elastomerssuch as unvulcanized or partially vulcanized, and/or fully vulcanizednatural rubber (NR). Other materials that may be used for the sealantlayer 106, as described above, may include but are not limited topolyisoprene (IR), styrene butadiene (SBR) or blends of SBR with NR orIR. Generally the materials selected will serve to swell into a cavityas large as that made by common projectiles 206, such as a 50 caliber or20 mm projectile, and smaller. The projectile 206 may comprise in-tactbullets, missiles, grenades, etc., and/or fragments thereof, and/orfragments from vehicle accidents/collisions.

This first portion 106A of the sealant layer 106 prevents the fluid 204from escaping or leaking through the wall system 200 of the cavity 210A.Swelling of the sealant layer 106 initiates from the fuel side andproceeds in an outward direction. Fiber from the fabric layers 104A,104B may also expand and fill the cavity 210 and may provide anadditional, yet moderate level of sealing of the liquid 204 compared tothe sealant layer 106. Meanwhile, the two elastomeric material layers102C and 102D remain broken by the projectile 206.

As understood by one of ordinary skill in the art, various differentsealing modalities may occur with the wall system 200. Because ofstrength, cut resistance and elongation of wall materials, the wallsystem 200 may stretch (bow) inward by a significant amount before theprojectile 206 penetrates into the volume containing the fluid 204. Whenthe wall system 200 recovers to essentially a flat surface, distancesbetween materials forming the wall system 200 may shorten, and thestretched fibers and elastomeric molecular strands within the wallsystem 200 may provide a puckering kind of seal around thecavity/wound/opening. This seal may include the sealant layer 106 whichmay facilitate autoadhesion.

FIG. 2F is a cross-sectional view of the wall system 200 of FIG. 2E inwhich, in some instances, it is possible the fluid 204 may react withthe sealant layer 106 causing the sealant layer 106 to further expandand to close the volume containing the fluid 204. In other instances orin addition to such a reaction between the fluid 204 and sealant layer106, the sealant layer 106 as well as others may be stretched from theprojectile 206 and this sealant layer 106 may provide a puckering kindof seal around the cavity/wound/opening due to inelastic expansion.Layer 106 is usually a hydrocarbon elastomer such as unvulcanized orpartially vulcanized, and/or fully vulcanized natural rubber (NR). Othermaterials that may be used for the sealant layer 106, as describedabove, may include but are not limited to polyisoprene (IR), styrenebutadiene (SBR) or blends of SBR with NR or IR.

In this exemplary embodiment, the first portion 106B has furtherexpanded into the cavity 210B that was created by the projectile 206when it passed through the wall system 200. As noted previously, thefirst portion 106B that has expanded into the cavity 210B because of itsreaction with the fluid 204, which may comprise a hydrocarbon fuel, mayprevent the fluid 204 from leaking through the cavity 210B formed by theprojectile 206.

Referring now to FIG. 3A, this figure is a diagram illustrating fibers105 receiving a polyurethane coating 301A. The coating 301A on thefibers 105 used to form a fiber layer 104C1 of FIGS. 1-2 may comprisesolvated aliphatic polyurethane that is applied during the fiber orfabric manufacturing process. As understood by one of ordinary skill inthe art, aliphatic is a general class of polyurethanes (excludingaromatic), which typically is easier to solvate than aromaticpolyurethanes. Other materials in addition to polyurethanes can be used,such as a resorcinol formaldehyde latex (RFL) and an isocyanate.

FIG. 3B is a diagram illustrating a fabric comprising fibers 105receiving a polyurethane coating 301B. The coating 301B on the fibers105 used to form fabric layer 104C of FIGS. 1-2 may comprise solvatedaliphatic polyurethane that is applied during the fiber or fabricmanufacturing process. FIG. 3B further illustrates a nozzle 305 that maybe used to apply the coating 301B of polyurethane to the fibers 105 ofthe fabric layer 104C2. Other ways or methods for applying the coating301 may be used other than those illustrated in FIGS. 3A-3B, such as byapplying the solvated polyurethane to the fabric layer 104C2 with aroller applicator or in a dip.

FIG. 4A is a cross-sectional view of one-half of a gas-impermeable,hollow preform or gas permeable solid preform 304, an elastomeric moldrelease layer 302, and a liner 202. The half-structure is noted bydashed line 402. As noted previously, the liner 202 layer may compriseany elastomeric material that will have a greater resistance tohydrocarbon fuel 204 than a polyurethane elastomer. Exemplary materialsinclude, but are not limited to, nylon, polyurethane, nitrile rubber,polysulfide, polyurea, polyvinylalchohol (PVA), Hydrogenated NitrileButadiene Rubber (HNBR), Epichlorohydrin rubber (ECO), and/orpolyvinylidene fluoride.

The preform 304 may comprise a molded or shaped object that has thegeneral shape and dimensions representing the inside volume of a fueltank. The preform 304 is gas-permeable or gas impermeable and it maycomprise a solid hard material, in that the preform preferably maysupport the weight of the wall portion 100 illustrated in FIG. 1 duringmanufacturing. Suitable materials for the preform 304 may include, butare not limited to, plaster, polyurethane, polyurea, polyester orpolystyrene foams. The preform 304 may be formed to have a shapesuitable for a mold or it may be cut and sculpted to a desired shape.According to some exemplary embodiments, the preform 304 may comprise agas-permeable solid structure such as illustrated in FIG. 7A (describedbelow) or the preform 304 may comprise a gas-impermeable hollowstructure such as illustrated in FIG. 7B (described below). Theinventive system 200 and method 500 may also employ foam board preforms304 as understood by one of ordinary skill in the art as an alternativeto the preform material 304A, 304B used for the gas-permeable structuresof FIG. 7A.

In the exemplary embodiment illustrated in FIG. 4A, the cross-sectionalshape of the gas-permeable, hollow preform 304 may comprise arectangular shape or a more complex shape. As noted above, othercross-sectional shapes are possible and are within the scope of thedisclosure described herein. Other cross-sectional shapes include, butare not limited to, oval, cylindrical, triangular, hexagonal (See FIGS.7A-7B), octagonal, and other like shapes or more complex convex and/orconcave shapes that may be conducive for use as fuel tanks on militarycrafts and/or other vehicles, such as, but not limited to, police cars,race cards, armored vehicles, etc.

Positioned between the liner 202 and the preform 304 is an elastomericmold release layer 302. The elastomeric mold release layer 302 may haveat least two purposes. First, it may serve as an elastomeric bag thatwill allow gaseous pressurization from inside the preform 304. Thegaseous pressure serves to expand the elastomeric mold release layer 302and subsequently push the uncured wall 100 structure against thesurfaces of mold 400A and 400B. In most cases, it is important that theelastomeric mold release layer 302 be leak tight during pressurization.Second, the elastomeric mold release layer 302 may serve as a moldrelease between the preform 304 and the liner 202. The elastomeric moldrelease layer 302 may comprise any conventional mold release material.Suitable mold release materials include, but are not limited to,silicone, elastomeric silicone, polyvinyl alcohol (PVA), polyolefin, oroil or grease mold release agents.

One of ordinary skill in the art will appreciate that the thicknessesillustrated in the cross-sectional view of FIG. 4A may have beenexaggerated for viewing purposes. The thicknesses of the liner 202, theelastomeric mold release layer 302, and the preform 304 may be variedwithout departing from the scope of the disclosure described herein.According to one exemplary embodiment, the liner layer 202 may have athickness of approximately 0.25 to approximately 1.0 mm, while theelastomeric mold release layer 302 may have a thickness of approximately2.0 to approximately 3.0 mm, and the preform 304 may have a thickness ofapproximately 25.4 to approximately 100.0 mm. The preform 304 may be amonolithic solid structure, a hollow structure, or a layered structure,for example.

FIG. 4B is a cross-sectional view of an intermediate product 300 thatcomprises the wall portion 100 of FIG. 1 in addition to the preform 304,the release layer 302, and liner 202 as illustrated in FIG. 4A. Theintermediate product 300 is characterized as such (“intermediate”)because the preform 304 and elastomeric mold release layer 302 are notutilized in the end product for containing a fluid 204, such as a fuel.The illustration of the intermediate product 300 of FIG. 4A is helpfulin understanding how a completed fuel tank or final product forming thewall system 200 as illustrated in FIGS. 2 and 4E-4E is manufactured.

FIG. 4C is a diagram illustrating how the intermediate product 300A ofFIG. 4B (which comprises the preform 304 and the elastomeric moldrelease layer 302 but no liquid 204) is positioned within a mold 400 andcoupled to a gaseous pressure source 403 according to one exemplaryembodiment. According to this exemplary embodiment, the intermediateproduct 300A has a hexagonal shape compared to the rectangularcross-sectional shape illustrated in FIG. 4B.

In the exemplary embodiment illustrated in FIG. 4C, the mold 400 maycomprise two halves 400A, 400B which are joined together. The two halves400A, 400 may be coupled together by any type of mechanical fastener,such as, but not limited to a hinge. Other types of molds 400, such as atwo piece compression mold 400, as well as other molding techniques maybe employed such as compression molding. The actual number of moldsections can be more than two and is dictated by each individual volumegeometry requirement. The mold section design also aids in the removalof the final product once the curing is complete. The mold 400 controlsthe dimension of the final product, which is the wallsystem/self-sealable volume 200 as illustrated in FIG. 1A.

Exemplary dimensions for the mold include, but are not limited to, about499.00 mm by about 555.00 mm by about 96.50 mm (or about 19.65 inches byabout 21.85 inches by about 3.80 inches). It is noted that the 19.65inches measurement corresponds to the 19.79 inches measurement for theself-sealing volume listed in Table 1 described below. It is furthernoted that the preform 304 does not control the final dimensions of thewall system/self-sealable volume 200.

TABLE 1 Exemplary self-sealing volume dimensions vs. conventionalmanufacturing methods Conventional Bladder Exemplary Bladder MeasurementMeasurement Measurement Measurement 1 2 1 2 Date Bladder Width 2″ Width5″ Date Bladder Width 2″ Width 5″ Measurement Measured SN from end fromend Measured SN from end from end  1 Sep. 10, 2012 Dec-54 17.59 17.48Sep. 19, 2012 398 19.76 19.78  2 Sep. 10, 2012 12-75890 17.59 17.53 Sep.19, 2012 381 19.8 19.82  3 Sep. 10, 2012 12-75862 17.57 17.6 Sep. 19,2012 382 19.8 19.81  4 Sep. 10, 2012 12-75871 17.52 17.58 Sep. 19, 2012383 19.79 19.78  5 Sep. 10, 2012 12-75894 17.58 17.5 Sep. 19, 2012 37919.77 19.79  6 Sep. 10, 2012 12-75859 17.61 17.6 Sep. 19, 2012 371 19.819.8  7 Sep. 19, 2012 12-75848 17.67 17.54 Sep. 19, 2012 400 19.78 19.79 8 Sep. 19, 2012 12-75888 17.65 17.38 Sep. 19, 2012 396 19.78 19.75  9Sep. 19, 2012 12-75933 17.59 17.4 Sep. 19, 2012 372 19.79 19.8 10 Sep.19, 2012 12-75892 17.57 17.41 Sep. 19, 2012 390 19.8 19.81 11 Sep. 19,2012 12-75885 17.58 17.6 Sep. 19, 2012 393 19.8 19.79 12 Sep. 19, 201212-75899 17.62 17.49 Sep. 19, 2012 380 19.78 19.8 13 Sep. 20, 201212-75907 17.59 17.46 Sep. 19, 2012 376 19.81 19.8 14 Sep. 20, 201212-75942 17.7 17.5 Sep. 19, 2012 375 19.8 19.79 15 Sep. 20, 201212-75924 17.61 17.49 Sep. 19, 2012 374 19.8 19.8 16 Sep. 20, 201212-75873 17.67 17.61 Sep. 19, 2012 377 19.81 19.8 17 Sep. 20, 201212-75920 17.51 17.59 18 Sep. 20, 2012 12-75884 17.45 17.39 19 Sep. 20,2012 12-75874 17.66 17.48 20 Sep. 20, 2012 12-75910 17.55 17.37 21 Sep.20, 2012 12-75788 17.66 17.39 22 Sep. 20, 2012 12-75895 17.68 17.35Average 17.6 17.49 19.79 19.79 Std Dev 0.061 0.086 0.014 0.016 % CV0.35% 0.49% 0.07% 0.08%

After curing of the intermediate product 300A within the mold 400 andlater removal of the preform 304 and elastomeric mold release layer 302,the cured structure forms the final wall system 200 of a self-sealingvolume as illustrated in FIG. 4E and FIG. 2. The mold 400 may comprise aheat source 410 for generating heat to apply to the intermediate product300A contained within the mold 400. A heat source 410 may comprise anytype of heat appropriate for molding or curing elastomeric structures asunderstood by one of ordinary skill in the art. Exemplary heat sources410 include, but are not limited to, conventional ovens, like convectionovens, microwave ovens, attached electrical strip heaters, autoclaves orattached tubing containing heated oil.

The mold 400 may also comprise a gaseous pressure source 403, like apump, for generating gaseous pressure to apply to the intermediateproduct 300A contained within the mold 400. Specifically, the gaseouspressure source 403 may be coupled to an inlet 503. The inlet 503 may becoupled to a metal fixture 507 that is contained within a nut ring 509.A nut ring 509 may comprise an access port for fuel filling, venting,and a fuel pump. Each nut ring 509 may be fitted with one metal fixture507. As understood by one of ordinary skill in the art, each metalfixture 507 is only used during bladder construction: It is removedafter manufacture and is not used to make connections in a vehicle.Multiple nut rings 509 may be used for redundancy and/or for differentconnections to the resultant self-sealing volume 100 which is designedto contain fuel.

Each self-sealing volume 100 may have one or more nut rings 509. Eachnut ring 509 may be fitted with cords or fabric flanges that extendradially into the elastomeric composite 100 to provide secure attachmentof the nut ring 509 to the self-sealing volume 100. A nut ring isdescribed and illustrated in U.S. Pat. No. 3,704,190, the entirecontents of which are hereby incorporated by reference. A nut ring mayhave a circular shape. However, it may have other shapes too, such as,but not limited to, oval, rectangular, rectangular with rounded edges,pentagonal, octagonal, etc.

A gaseous pressure source 403 may comprise any type of gaseous pressureappropriate for forming a shaped part of elastomeric structures asunderstood by one of ordinary skill in the art. Exemplary gaseouspressure sources 403 include, but are not limited to, compressed airfrom a compressed cylinder or from a conventional air compressor, orcompressed nitrogen, argon, carbon dioxide or helium from a compressedcylinder.

As noted previously, the elastomeric mold release layer 302 forms a gastight seal around the preform 304 when the elastomeric mold releaselayer 302 is inflated by the gaseous pressure source 403. Theelastomeric mold release layer 302 will expand the elastomeric materiallayers 102 when the elastomeric mold release layer 302 is inflated witha gas from the gaseous pressure source 403. The amount of pressureprovided by the gaseous pressure source 403 is generally between about2.0 psi to about 80.0 psi, and preferably between about 10.0 psi toabout 40.0 psi, and more preferably at about 20.0 psi. However, otherpressures may be used as understood by one of ordinary skill in the artand are within the scope of this disclosure.

FIG. 4D is a diagram illustrating a cured intermediate product 300Cafter the intermediate product 300C is removed from the mold 400 of FIG.4C, disconnected from the inlet 503 and gas pressure source 403, andafter the intermediate product 300C has been cured. The intermediateproduct 300C may have any three dimensional shape including regularcubic square or rectangular cross-sectional shape or an irregular cubicquadrilateral shape or a complex multisided three dimensional shape. Inthe exemplary embodiment illustrated in FIG. 4D, the intermediateproduct 300C has a hexagonal shape.

The intermediate product 300C is characterized as such (“intermediate”)because it comprises the elastomeric mold release layer 302 and thepreform 304 (internally), which are not illustrated in this figure butare illustrated in FIGS. 4A-4B. The view of FIG. 4D is an external oneof the intermediate product 300C such that the internal layers, such asthe elastomeric mold release layer 302 and preform 304, are not visible.

FIG. 4E is a diagram illustrating the formation of the completed product200 of FIGS. 2A-2F by removing the preform 304 and the release layer304. The preform 304 and release layer 302 may be removed from theintermediate product 300C, as disclosed below.

The preform 304 and elastomeric mold release layer 302 may be removedafter the intermediate product 300C has been fully cured and cooled.These two structures 304, 302 may be removed by breaking them into smallpieces or chunks, or a single extended piece, and removing them throughnut ring 509. The preform 304 may be smaller relative to (have outerdimensions which are less than) the finished product 200 since thepreform 304 is filled with a fluid, like air, such that the mold releaselayer 302 expands from the fluid. The fluid may include a gas that isused while the finished product 200 is curing. The preform 304 usuallydoes not change in size/dimensions when the fluid is provided inside thepreform 304 to inflate the mold release layer 302.

Usually, the elastomeric mold release layer 302 is removed with thepreform 304 illustrated in FIG. 4E. Then, the preform 304 may be removedthrough the nut ring 509 of the finished product 200. The nut ring 509usually has a round shape, but other shapes may be employed asunderstood by one of ordinary skill in the art. Once these structures304, 302 are completely removed, the finished and completed product 200is formed as illustrated in FIG. 1A.

FIG. 4F1 is a cross-sectional view of a self-sealing volume 200 in theform of a fuel tank illustrating the individual composite layers alongwith paths 411 of air escape according to one exemplary embodiment. FIG.4F1 has a breather structure 409. The wall system/volume 200 comprises awall 100 and a liner 202 which will be described in more detail below.The self-sealing wall system 200 may contain a fluid 204 (See FIG. 1A),such as, but not limited to, a hydrocarbon fuel.

Other layers of the wall system or volume 200 may include a releaselayer 302 (which is used during formation of the volume 200 but laterdiscarded after formation of volume 200), an elastomeric material andfabric 407, and sealant layer 106. The sealant layer 106 usually coversthe entire (100%) of the surface area for the volume 200. The sealantlayer 106 is responsible for sealing any punctures in the volume 200should a projectile strike and penetrate through the wall 100 of thevolume 200. Further details of the elastomeric material and fabric 407will be described below in connection with FIG. 4F2. Similar to theother exemplary embodiments of the volume 200, the volume 200 of FIG.4F1 may include a nut ring 509 as described above.

In the exemplary embodiment illustrated in FIG. 4F1, the volume 200comprises three elastomeric material and fabric layers 407A, 407B, 407Cin each corner that forms the first breather structure 409A.Specifically, the first breather structure 409A comprises the followinglayers along the geometrical ray AB as follows (starting from point Aextending towards point B of ray AB): the release layer 302 (which isdiscarded after formation of the preform and prior to filling the volume200), the liner 202, the first elastomeric material and fabric 407A, asecond elastomeric material and fabric 407B, a sealant layer 106, and athird elastomeric material and fabric 407C.

The first breather structure 409 of the exemplary embodiment illustratedin FIG. 4F1 is formed in such a way that a first gap 479A between pointsC and D located on respective different sealant layers 106 is formed andfilled with the second elastomeric material and fabric 407B. A fluid formanufacturing the volume 200, such as air, may be allowed to escape thevolume 200 by following fabric path 411 which exists within elastomericmaterial and fabric layers 407A, 407B, and 407C. A second gap 479B isformed similarly on the other side of the first breather structure bythe second elastomeric material and fabric 407B.

An edge portion or overlap portion O of the sealant layer 106 (whichlies on top of an elastomeric material and fabric 407) in each breatherstructure 409 may have a length of between about a 0.25 of an inch toabout 2.00 inches. The sealant layer 106 may have a thickness of betweenabout 0.02 of an inch to about 0.12 of an inch. The elastomeric materialand fabric layers 407 may each have a thickness between about 0.005 ofan inch to about 0.03 of an inch.

The overall length (L) of the volume 200 may comprise a magnitude ofabout 20.0 inches, while the overall height (H) of the volume 200 maycomprise a magnitude of about 10.0 inches. The volume 200 may have widthdimension (not visible) having a magnitude of about 22.0 inches. Asnoted previously, the shape of the volume 200 may be varied withoutdeparting from the scope of this disclosure. Therefore, other magnitudesfor the length (L), width, and height (H) may be possible with differentgeometrical shapes for the volume 200.

Further, one of ordinary skill the art will recognize that the numberand size of the layers may be varied without departing from the scope ofthe present disclosure. That is, fewer or a greater number of layerswith different thicknesses may be used for a particular embodimentwithout departing from the scope of the technology described herein.

In each of the figures of this disclosure, the breather structure 409may appear to have a thickness and size which are greater than arespective side of the volume 200. In other words, each breatherstructure 409 may appear to be “bulging” relative to the sides of thevolume 200 which do not have a breather structure 409. However, thefigures of this disclosure with respect to the breather structure 409have been greatly exaggerated. In the actual final volume 200, eachbreather structure 409 and its relative thickness are usually verydifficult to detect with the naked eye.

FIG. 4F2 is a side view of an elastomeric material and fabric 407 thatis depicted in FIG. 4F1. The elastomeric material and fabric 407 maycomprise three layers sandwiched together: a first elastomeric materialmatrix layer 102 (as described above in connection with FIGS. 1-3), afabric or fiber layer 104, and a second elastomeric material matrixlayer 102. The first and second elastomeric materials 102 envelope orsandwich the fabric layer 104 therebetween. The elastomeric materials102 have been described in detail above. In many embodiments, the twoelastomeric materials 102 are absorbed into the fabric or fiber layer104 instead of encasing/circumscribing the fabric layer 104.

Each elastomeric material/matrix layer 102 may comprise at least oneeach of styrene butadiene rubber dispersions, nitrile butyl rubberdispersions, polychloroprene dispersions, polyurethane dispersions,polyurea dispersions, solvated polyureas, solvated polyurethanes,solvated nitrile butyl rubber, solvated polychloroprene, silicones,polysulfides, polyurethane ureas, epoxy, polyester, silicone. Eachfabric layer 104 may comprise one or more layers of fabrics made from atleast one of nylon, aramid, polyester polypropylene and polyethylene.Each fabric layer 104 may also comprise cords in which each cord has adiameter of between about 0.0624 of an inch to about 0.25 an inch. Eachelastomeric material and fabric 407 may have a weight between about 2.0oz/square yard to about 36.0 oz/square yard. The fabric types mayinclude, but are not limited to, woven materials, non-woven materials,and knitted materials.

FIG. 4G is a cross-sectional view of a corner of a self-sealing volume200 illustrating an alternative layup pattern where one or morestructural fabric plies are located on one side of the sealant layer106. The mold release layer 302 is not present in this embodiment: ithas been removed. The sequence of layers for the exemplary embodimentillustrated in FIG. 4G are as follows using geometrical ray AB as areference for the sequence of materials that form the breather structure409B of FIG. 4G: liner 202, a first elastomeric material and fabric407A, a second elastomeric material and fabric 407B, sealant layer 106,and a third elastomeric material and fabric 407C.

Relative to the first breather structure 409A illustrated in FIG. 4F1,the second breather structure 409B illustrated in FIG. 4G has only asingle gap 479 formed between the two sealant layers 106 by the secondfabric 407B for a respective corner region of the volume 200. A fluid orgas, like water, solvent or air, may flow along fabric path 411.Meanwhile, the sealant layer 106 for the first breather structure 409Ahas two gaps and two fabric paths 411 per corner illustrated in FIG.4F1.

FIG. 4H is a cross-sectional view of a corner of a self-sealing volume200 illustrating an alternative layup pattern where one of the fabriclayers 407A1 is extended in a continuous manner around the sealant layer106 to meet the outer fabric layer 407A2. The mold release layer 302 isnot present in this embodiment: it has been removed. Following the firstfabric layer 407A1 along solvent, water or air escape path 411, thefirst fabric layer 407A1 has an extension region 407EX that continuestowards the outer layer 407A2. With this configuration, another singlegap 479, like the exemplary embodiment illustrated in FIG. 4G, is formedfor this breather structure 409C.

FIG. 4I is a side view of a corner of a self-sealing volume 200illustrating a view of outside layers down to the sealant layer 106where layers inside sealant layer 106 are not shown and provide analternative lay-up pattern where the sealant layer 106 has beenperforated with apertures 419. The sealant layer 106 is subsequentlycovered with fabric elastomeric material and fabric layers 407A and theareas where apertures 419 are located are covered with sealant patches106P that are larger than the original holes 419. A final elastomericmaterial and fabric 407A (not illustrated) covers sealant patches 106Pand elastomeric material and fabric 407.

The apertures 419 can be any shape, such as, but not limited to,circular, elliptical, rectangular, square, slits and other similargeometric shapes. The size of the apertures 419, such as diameters forround apertures 419, may range between about 0.05 of an inch to about1.0 inch. The sealant patches 106P and corresponding elastomericmaterial and fabric 407 covering the apertures 419 are covered with afinal elastomeric material and fabric 407 as indicated with the dashedline 407 in this FIG. 1.

FIGS. 4J1-4J5 are side views of the formation of a self-sealing volume200 using a straight wall lay-up technique in which the breatherstructure is located in a lateral side of the volume 200 instead of acorner of the volume 200. Any of the build configurations described inthis disclosure may have breather structures located in sides of thevolume 200, in corners of the volume 200, or in combinations thereof.

With a lay-up technique, the layers illustrated in each figure areapplied in sequence. The elastomeric material layers 102 (part ofelastomeric material and fabric 407) provide the necessary tack/adhesiveto hold all structures together before curing. The layers in FIGS.4J1-4J5 are applied by hand using tools such as a spatula or roller tosmooth out and remove as much trapped air as possible.

Specifically, FIG. 4J1 is a side view of an intermediate self-sealingvolume 200 illustrating an inner, first elastomeric material and fabric407 applied over a liner layer 202 (not visible in this FIG. 4J1 but seeFIG. 4F1). After the first elastomeric material and fabric 407 isapplied over the liner 202, then in FIG. 4J2, a sealant layer 106 isapplied.

Specifically, and referring to FIG. 4J2, a side view of an intermediateself-sealing volume 200 illustrates the sealant layer 106 applied with agap 413 over the elastomeric material and fabric 407 of FIG. 4J1. Withinthis gap 413, the elastomeric material and fabric 407 is visible. Thegap 413 may have a width dimension of between about 0.10 of an inch toabout 3.00 inches. However, other widths are possible and are within thescope of this disclosure.

Referring now to FIG. 4J3, this figure is a side view of an intermediateself-sealing volume 200 illustrating a rectangular breather fabric 407Rapplied over the gap 413 (illustrated in FIG. 4J2). This rectangularbreather fabric 407R may have a length dimension (L1) of between about0.5 of an inch to about 4.00 inches that extends beyond gap 413 oneither side of gap 413 (about 0.25 to about 1.00 inch on either side ofsealant patch 106P) which usually is less than the overall length of thevolume 200.

Next, FIG. 4J4 is a side view of an intermediate self-sealing volume 200illustrating a sealant patch 106P applied over the gap 413 andrectangular breather fabric 407R of FIG. 4J3. The sealant patch 106P mayhave a length dimension (L2) of approximately between about 0.25 of aninch to about 1.00 inch that extends beyond gap 413 but less than fabric407R on either side of fabric 407R (about 0.25 to about 1.00 inch lesson either side of fabric 407R) which usually is less than the overalllength of the volume 200] And FIG. 4J5 is a side view of an intermediateself-sealing volume 200 illustrating an outer, second elastomericmaterial and fabric 407 applied over the sealant patch 106P and sealant106 of FIG. 4J4.

FIGS. 4K1-4K7 are views of the formation of a self-sealing volume 200using a calendared sealant patch technique. Specifically, FIG. 4K1 is aside view of an intermediate self-sealing volume 200 illustrating aninner, first elastomeric material and fabric 407 positioned over a linerlayer 202 (not visible in this FIG. 4K1 but see FIG. 4F1).

FIG. 4K2 is a side view of an intermediate self-sealing volume 200illustrating the sealant layer 106A or a calendared sealant 106A appliedwith a gap 413 over the elastomeric material and fabric 407 of FIG. 4K1.For forming a calendared sealant 106A, the sealant 106 is previouslylaminated directly to a fabric 407 by passing the sealant 106 and fabric407, stacked together, between solid metal rolls under pressure.

The gap 413 of FIG. 4K2 may have the same dimensions described abovewith respect to the exemplary embodiment illustrated in FIG. 4J. Similarto FIG. 4J2 described above, within this gap 413, the elastomericmaterial and fabric 407 is visible. Next, FIG. 4K3 is a side view of anintermediate self-sealing volume 200 illustrating a calendared sealantpatch 106CP applied over the gap 413 and sealant 106A of FIG. 4K2.Usually, calendered sealant patch 106CP is applied so that fabric sideis positioned on sealant layer 106A. The calendared sealant patch 106CPmay have a length dimension (L3) of approximately between about 0.5 ofan inch to about 4.00 inches that extends beyond gap 413 on either sideof gap 413 (about 0.25 to about 1.00 inch on either side of gap 413)].Next, FIG. 4K4 is a side view of an intermediate self-sealing volume 200illustrating an outer, second elastomeric material and fabric 407applied over the calendared sealant patch 106CP and sealant layers 106Aof FIG. 4K3.

FIG. 4K5 is a cross-sectional, top view of the calendared sealant patchembodiment of FIG. 4K4. In this exemplary embodiment illustrated in FIG.4K5, the gap or absence of material 413 between sealant layers 106A ismore visible. The inner most elastomeric material and fabric 407A facesthe inside of the volume 200 while the outermost elastomeric materialand fabric 407B faces an outside or exterior of the volume 200. As notedpreviously, the gap 413 allows a manufacturing fluid, such as water,solvent or air, to permeate through the first elastomeric material andfabric 407A, through the gap 413 between the sealant layers 106 andthrough the calendared patch layer 106CP and outermost elastomericmaterial and fabric 407B corresponding to directional arrow A in thisFIG. 4K5.

FIG. 4K6 is a side view of the calendared sealant patch 106CP of FIGS.4K3 and 4K5 alone. FIG. 4K7 is a cross-sectional view of the calendaredsealant patch 106CP illustrated in FIG. 4K6. Like the sealant layer 106described above, the calendared sealant patch 106CP may have a thicknessof between about 0.02 of an inch to about 0.3 of an inch. The calendaredsealant patch 106CP may comprise a fabric 417 made of nylon, polyester,polypropylene, and an aramid having exemplary weights between about 1.0ounces to about 32.0 ounces. The fabric can be woven, nonwoven, or knit.The sealant layer or side 106 is pressed on or calendared onto thefabric 107. Lower weight fabric may be employed such as nylon fabrichaving exemplary weights between about 1.0 ounce to about 12.0 ounces,and preferably, about 2.0 ounces.

FIGS. 4L1-4L5 are side views of the formation of a self-sealing volume200 using a breather fabric strips or cords technique. FIG. 4L1 is aside view of an intermediate self-sealing volume 200 illustrating aninner, first elastomeric material and fabric 407 positioned over a linerlayer 202 (not visible in this FIG. 4J1 but see FIG. 4F1). Next, FIG.4L2 is a side view of an intermediate self-sealing volume 200illustrating the sealant applied with a gap 413 over the elastomericmaterial and fabric 407 of FIG. 4L1. This gap 413 of FIG. 4L2 may havethe same dimensions described above with respect to the exemplaryembodiment illustrated in FIG. 4J. Similar to FIG. 4J2 described above,within this gap 413, the elastomeric material and fabric 407 is visible.

FIG. 4L3 is a side view of an intermediate self-sealing volume 200illustrating breather fabric strips 407S applied over the gap 413illustrated in FIG. 4L2. These strips 407S may have a length dimensionof approximately between about 0.25 of an inch to about 4.00 inches anda width dimension of approximately between about 0.25 of an inch toabout −2.0 inches. The number of strips 407S is usually between about 4and about 20, depending upon size.

FIG. 4L4 is a side view of an intermediate self-sealing volume 200illustrating a sealant patch 106P applied over the gap 413 and breatherfabric strips 407S, as well as portions of the sealant layer 106A ofFIG. 4L3. Similar to FIG. 4J4, the sealant patch 106P may havedimensions similar to the sealant patch 106P described above inconnection with FIG. 4J4. FIG. 4L5 is a side view of an intermediateself-sealing volume 200 illustrating an outer layer of the elastomericmaterial and fabric 407 applied over the sealant patch 106P and sealant106A of FIG. 4J4.

These FIGS. 4J, 4K, and 4L illustrate exemplary sequences of steps thatmay be taken in order to produce the breather structures 409 asillustrated in FIGS. 4F1, 4G, and 4I. However, one of ordinary skill theart will appreciate that other steps may be taken and other sequences ofsteps may be made while still creating the breather structures 409 asillustrated in FIGS. 4F1, 4G, and 4I.

Referring now to FIG. 5A, this figure is a flowchart illustrating amethod 500 for forming a self-sealing volume 200 according to anexemplary embodiment. Routine block 502 is the first block of method500. In routine or sub-method block 502, a preform 304 as illustrated inFIG. 4A and further illustrated in FIGS. 7A-7B may be generated. Apreform 304 typically has a three dimensional shape as illustrated inFIGS. 4C, and 7A-7B. Further details of routine block 502 will bedescribed below in connection with FIGS. 7A-7B, and FIGS. 8-9. Thepreform 304 may or may not have a symmetrical shape. At the end of block502, a metal fixture 507 is mounted within the opening 405 of thepreform mold.

Next, in block 505, the preform 304 may be coated with an elastomericmold release material 302 as illustrated in FIG. 4A. As notedpreviously, this elastomeric mold release material may comprisesilicone, elastomeric silicone, polyvinyl alcohol (PVA) or polyolefinmold release agents. Specifically, an elastomeric release material 302,such as SMOOTH-ON-EZ-SPRAY™ SILICONE® 20 silicone (which is a 20 Shore Asilicone elastomer) may be sprayed or otherwise coated over the surfaceof the preform 304.

In block 510, the elastomeric mold release material 302 may be coatedwith a volume liner 202. Liner 202 may comprise any elastomeric materialthat will have a greater resistance to hydrocarbon fuel 204 than apolyurethane elastomer. Exemplary materials for the liner material 202include, but are not limited to, polyurethane, polyurea, nitrile rubber,polysulfide, polyvinylalchohol (PVA), hydrogenated nitrile butadienerubber (HNBR), epichlorohydrin rubber (ECO), and polyvinylidenefluoride. The inner liner 202 may comprise a polysulfide, such as PRCRAPID SEAL 655™ aliphatic polysulfide sold by PRC-DeSoto International,Inc. Or the liner 202 may comprise another fuel resistant elastomericmaterial. It can be sprayed in or on, coated or laid in as a sheet.

In block 510, a nut ring 509 may be mounted into the opening 405 of thepreform mold containing the metal fixture 507 as understood by one ofordinary skill in the art. Each nut ring 509 is fitted with cords orfabric flanges that extend radially into the elastomeric composite 100to provide secure attachment of the metal nut ring 509 to theself-sealing volume 100. These cords or fabric flanges are typicallyfitted on each nut ring 509 prior to starting method 500.

Alternatively, the volume 300A can be fabricated without the volumeliner 202 which can be added in a subsequent step after the volume 300Ais cured and the preform 304 and the elastomeric mold release layer 302have been removed.

In an alternate exemplary embodiment, a path 522 is illustrated with adashed line to convey that it's optional. It may be followed if theinner liner layer 202 is applied by spraying. Next, in optional block515 (illustrated with dashed lines), the fabric or fiber layer 104 maybe formed by coating the layer 104 with a solvated polyurethane.Alternatively, fabric or fiber layer 104 may be coated with a resorcinolformaldehyde resin or a solvated isocyanate.

Usually, this coating of the fiber layer 104 is completed as a separatestep during manufacture of the fabric and it may not be part of theconstruction of the self-sealing container. Subsequently, in optionalroutine or submethod 520 (illustrated with dashed lines), theelastomeric material layer 102 may be created. Routine 520 has beenhighlighted with dashed lines to denote it is optional and would not beused if a non-cross-linked version of the polyurethane dispersion (SeeExample 2 described below) in the three examples noted below is selectedfor the elastomeric material layer 102. Further details of optionalroutine or submethod 520 are described below in connection with FIG. 6.

Next, in block 525, a first layer of the elastomeric material 102D asillustrated in FIG. 4B of the intermediate product 300 is applied to theliner 202. The elastomeric material 102D is also applied to fabric layer104B. The method 500A then continues to block 535 of FIG. 5B.

FIG. 5B is a continuation flowchart of FIG. 5A illustrating the method500B for forming a self-sealing volume 200 according to an exemplaryembodiment. In block 535, a first coated fabric or fiber layer 104B isapplied to the first layer 102D of the elastomeric material 102D asillustrated in FIG. 4B. In an alternative exemplary embodiment, theelastomeric material 102D may be applied to the coated fabric 104B andthen these two layers 102D, 104B may be applied to the liner layer 202in which the elastomeric material 102D is sandwiched between the fabriclayer 104B and the liner layer 202.

Next, in optional block 537, (illustrated with dashed lines), the coatedpreform 304 having the wall structure illustrated in FIG. 4B is debulkedso that the elastomeric material remains uniform throughout the fabricand excess water or solvent is removed. This may be accomplished byvacuum bagging and heating to the temperature at which evaporation ofwater will be facilitated, typically above about room temperature toabout 120° C., and preferably below about 100° C. As it dries, thedispersion from layer 102 will coalesce in a time period of betweenabout 60.0 minutes to about 360.0 minutes, and preferably in about 180.0minutes.

In block 540, a second layer of the elastomeric material 102C is appliedto the first coated fabric or fiber layer 104B of FIG. 4B. In block 545,sealant layer 106 may have a primer or adhesion activator coated onprior to application. Then, the sealant layer 106 is applied to thesecond layer of the elastomeric material 102C as illustrated in FIG. 4B.As noted previously, the sealant layer 106 may comprise natural rubberor partially vulcanized natural rubber (NR) (having less than about 1%sulfur). Other materials that may be used include polyisoprene (IR),styrene butadiene (SBR), blends of SBR with NR or IR, and low durometerpolyurethanes (approximately Shore A less than 70). In block 550, athird layer of the elastomeric material 102B is applied to the sealantlayer 106.

In block 555, a second coated fabric or fiber layer 104A is applied tothe third layer of the elastomeric material 102B as illustrated in FIG.4B. The method 500B then continues to block 575 of FIG. 5C.

FIG. 5C is a continuation flowchart of FIG. 5B illustrating the method500C for forming a self-sealing volume according to an exemplaryembodiment. Next, in optional block 575, (illustrated with dashedlines), the coated preform 304 having the wall structure illustrated inFIG. 4B may be debulked so that the elastomeric material remains uniformthroughout the fabric and excess water or solvent is removed. This isaccomplished by vacuum bagging and heating to the temperature at whichevaporation of water will be facilitated, typically above about roomtemperature to about 120° C., and preferably below about 100° C. As itdries, the dispersion from layer 102 will usually coalesce in a timeperiod of between about 60.0 minutes to about 360.0 minutes, andpreferably in about 180.0 minutes. Next, in block 580, the coatedpreform 304 comprising the intermediate products 300A as illustrated inFIG. 4C is placed into a mold 400.

Subsequently, in block 585, the preform 304 forming the intermediateproducts 300A is closed within the mold 400 as illustrated in FIG. 4C.In block 590, heat and pressure may be applied to the mold 400 from heatsource 410 and gas pressure source 403 in order to cure the preform 304or intermediate product 300A to form the cured, single intermediateproduct 300C as illustrated in FIG. 4D. The gas pressure source 403 mayfill the preform 304 while expanding the mold release layer 302 suchthat layer 302 pushes the composite wall structure/system 100 againstthe heated mold 400 during curing. This pressure can be between 5-100psi, preferably between 10-40 psi, and preferably 20 psi. Specifically,the gas pressure source 403 may inflate the elastomeric mold releaselayer 302 that is on the outside of the gas-permeable preform 304 sothat the wall structure 100 (FIG. 1B) is pressed against the heated mold400. Temperatures for curing can be between 83° C. to about 177° C., butpreferably 149° C. Once the structure 300A of FIG. 4C cures intostructure 300C of FIG. 4D, the fixture 507 may be removed from the nutring 509.

In block 591, an outer fuel liner 103 may be applied to the secondcoated fabric or fiber layer 104A as illustrated in FIG. 4B. The outerfuel liner 103 may comprise any elastomeric material that will have agreater resistance to hydrocarbon fuel 204 than a polyurethaneelastomer. Exemplary materials for the outer fuel liner material 103include, but are not limited to, polyurethane, polyurea, nitrile rubber,polysulfide, polyvinylalchohol (PVA), hydrogenated nitrile butadienerubber (HNBR), epichlorohydrin rubber (ECO), and polyvinylidenefluoride. The outer liner 103 may comprise a cross-linked polyurethaneas outlined in submethod 520 of FIG. 5A. Or the outer liner 103 maycomprise another fuel resistant elastomeric material. It can be sprayedon, coated or laid in as a sheet. Final cure of the outer fuel liner 103can take place by heat from a conventional oven, an autoclave, amicrowave oven or from a press, or alternative ways as understood by oneof ordinary skill in the art. Temperatures for curing can be between 52°C. to about 149° C., but preferably 83° C.

In block 592, the inlet 503, metal fixture 507, preform 304 andcorresponding elastomeric mold release layer 302 attached thereto maythen be removed from the resultant cured volume 300C as illustrated inFIG. 4E to form the completed wall system or self-sealing volume 200 asillustrated in FIG. 4E. Specifically, the preform 304 and correspondingelastomeric mold release layer 302 may be broken into small piecesrelative to the entire cured volume or wall system 200 and removedthrough nut ring 509 that penetrates through the volume formed by thewall system 200 as illustrated in FIG. 4E.

Next in block 593, if a volume liner 202 was not added in block 510, avolume liner 202 can be sprayed into the completed volume 300C so that aliquid impermeable coating completely covers the inside of the volume300C. Liner 202 may comprise any elastomeric material that will have agreater resistance to hydrocarbon fuel 204 than a polyurethaneelastomer. Exemplary materials for the liner material 202 include, butare not limited to, polyurethane, nitrile rubber, polysulfide, polyurea,polyvinylalchohol (PVA), Hydrogenated nitrile butadiene rubber (HNBR),epichlorohydrin rubber (ECO) and polyvinylidene fluoride.

Next, in block 594, the volume formed by the wall system 200 may befilled with a fluid For example, the fluid may comprise a hydrocarbonfuel, such as gasoline or diesel. The method 500 then ends after block594.

FIG. 6 is a flowchart illustrating optional routine or submethod 520 forcreating an elastomeric material layer 102 according to an exemplaryembodiment. Routine 520 of FIG. 5A has been highlighted with dashedlines to denote it is optional and would not be used if anon-cross-linked version of polyurethane of the three examples notedbelow (See Example 2 described below) is selected for the elastomericmaterial layer 102. However, if using a cross-linked polyurethane isdesired, then this routine 520 may be followed. Block 605 is the firststep of submethod or routine 520.

In block 605, a polyurethane dispersion having a predetermined molecularweight with a crosslinking agent is prepared. Normally, any of thewell-known water dispersible polyurethanes useful for coating textilesmay be utilized for the elastomeric material layer 102. Urethanes oftoluene diisocyanate and methylene diphenyldiisocyanate are suitableexemplary materials as they are frequently used for coating textiles.The crosslinking agent can be any polydiisocyanate that is waterdispersible. Water dispersible polydiisocyanates based on hexamethylenediisocyanate are suitable exemplary materials as they are frequentlyused as crosslinking agents for polyurethane dispersions. The amount ofwater dispersible polydiisocyanate used is about 2 to 5 weight percentbased on the polyurethane dispersion. The submethod then returns toblock 525 of FIG. 5A.

Referring now to FIG. 7A1, this figure illustrates a cross-sectionalview of a device 400C, 400D for forming flexible molds 400E, 400Faccording to an exemplary embodiment. The device 400C, 400D may comprisetwo flexible molds shells that are used to create flexible molds 400E,400F. In the exemplary embodiment illustrated in FIG. 7A1, the two moldshells have the cross-sectional shape of one half of geometric hexagon.As noted previously, inventive method and system are not limited to theshapes described or illustrated in this disclosure. Other shapes arepossible as understood by one of ordinary skill in the art.

The two rigid mold shells 400C, 400D may comprise materials such as, butnot limited to plaster, wood, molded plastic, clay, fiberglasscomposite, etc. One of the mold shells 400C, 400D may comprise anaperture or opening 405 such as mold shell 400D. This opening 405 willbe used for a fixture 507 as will be described in further detail below.

As mentioned previously, FIGS. 7A and 7B illustrate one of severaloptions for producing a preform. Other options/embodiments covered bythis disclosure, but not illustrated, include three dimensional preformmolds cut from a block of polyethylene, polystyrene foam or othersimilar material. In these other, alternative embodiments, the preformmolds may be rigid (not flexible) as understood by one of ordinary skillin the art.

As illustrated in FIG. 7A1, the flexible molds 400E, 400F will generallyhave a shape that corresponds to the shape of the two rigid mold shells400C, 400D. The flexible molds 400E, 400F previously made of a materialsuch as, but not limited to, silicone, polyethylene, or polypropylene.

FIG. 7A2 is a cross-sectional view of the flexible molds 400E, 400Fformed from the device 400C, 400D of FIG. 7A1 according to an exemplaryembodiment. According to this exemplary embodiment, the two rigid moldshells 400C, 400D have been removed so that only the flexible molds400E, 400F each having one half of a hexagonal cross-sectional shaperemain. As noted previously, one of the flexible molds 400F has anopening 405.

FIG. 7A3 is a cross-sectional view of preform material 304A, 304Bpositioned within the flexible molds 400E, 400F of FIG. 7A2 according toan exemplary embodiment. According to this exemplary embodiment, thepreform material 304A, 304B will form a gas-permeable, solid structure.The preform material 304A, 304B may be generated by mixing equal partsof a diisocyanate such as sold under the tradename SMARTFOAM A and apolyol such as SMARTFOAM B. These mixtures are poured into thefabricated two piece molds 400E, 400F that usually have insidedimensions which correspond to the required outside dimensions of thepreform 304. Once the preform material 304B of the mold 400F curesslightly (or prior to pouring of the preform material 304B) the mold400F may be fitted with a metal fixture 507.

The metal fixture 507 of FIG. 7A3 will provide ingress for air and willserve as a mounting for the preform 304 during layup. The location ofthe metal fixture 507 is selected to coincide with the location of a nutring 509 in the finished self-sealing volume 100.

FIG. 7A4 is a cross-sectional view of the two halves of a gas-permeable,solid preform 304A, 304B generated from the flexible molds 400E, 400F ofFIG. 7A3 according to an exemplary embodiment. In this exemplaryembodiment, the flexible molds 400E, 400F have been removed such thatthe gas-permeable, solid preform halves 304A, 304B remain. The secondhalf 304B has the metal fixture 507 as described above. These halves304A, 304B may be rotated as indicated by the directional arrows untilcompletely cured. Rotation may or may not be used. In other embodiments,the halves 304A, 304B are not rotated. The material described above forthe preforms 304A, 304B generally cure at standard room temperature andpressure as understood by one of ordinary skill in the art.

FIG. 7A5 is a cross-sectional view of the two halves of thegas-permeable, solid preform 304A, 304B put/mated together according toan exemplary embodiment. The fully cured, two halves 304A, 304B aremated together by adhesives. Usually, adhesives that do not containsolvent or water may be employed. Such adhesives include, but are notlimited to, epoxies or two part urethanes.

The resultant gas-permeable solid preform 304D may be characterized as aurethane preform 304D. This FIG. 7A5 also illustrates a coating 707 thatmay be applied to the preform surface to provide a smooth, rigid surfacefor build-up. Materials used for the coating 707 may include, but arenot limited to, a rigid polyurethane such as FEATHERLITE® brandlow-density urethane casting resin.

FIG. 7A6 is a cross-sectional view of the gas-permeable, solid preform304D after apertures or holes 701 have been created within the preform304D according to an exemplary embodiment. Any number of holes 701 maybe created within the solid preform 304D. The holes 701 may be createdwith machines such as, but not limited to, drills or lasers. The holes701 may be randomly positioned or positioned at evenly spaced intervalsas understood by one of ordinary skill in the art. The holes 701 willhelp a fluid originating from the gaseous pressure source 403 to exitthe preform 304D in order to properly inflate the release layer 302 asdescribed above. Holes 701 are usually only needed if an impermeableskin (i.e. like FEATHERLITE® brand low-density urethane casting resin)is applied to the outside of the foam/solid preform 304D but can be usedin any foam/solid preform 304D. Holes 701 are also usually needed inclosed-cell foams forming the preform 304D which generally do notrequire the use of an outer shell (i.e like FEATHERLITE® brandlow-density urethane casting resin). The depth of the holes 701 onlyneed to penetrate the FEATHERLITE® brand low-density urethane castingresin, or close-cell foam skin but can penetrate further into the foam.The foam has pores which may connect to the holes 701. An open cell foamused for the solid preform 304D may not require any holes 701 in someinstances.

The outer surface of the solid preform 304D may be sanded and finishedto the desired internal dimension that may be used for the self-sealingvolume 100 once formed, as understood by one of ordinary skill in theart. “Finished,” as described herein, means to sand and smooth so as toremove cracks, seams and imperfections as understood by one of ordinaryskill in the art.

Referring now to FIG. 7B1, this figure illustrates a cross-sectionalview of a solid mold 400G, 400H for forming a gas-impermeable, hollowpreform 304C according to an exemplary embodiment. This solid mold 400G,400H is “solid” in the sense that its walls may comprise a solidmaterial. However, the solid mold 400G, 400H may comprise a hollowinterior 400Z so that a hollow type preform 304C (SEE FIG. 7B5) may begenerated. The solid molds 400G and 400H are part of the submethod 502Bdescribed below in FIG. 9. Submethod 502B may comprise a form of rotocasting (also known as rotacasting) as understood by one of ordinaryskill in the art. Such rotacasting may use self-curing resins inunheated molds, and may share slow rotational speeds that are in commonwith rotational molding.

Similar to the exemplary embodiment illustrated in FIG. 7A, a portion,such as one half, of the solid mold 400G, 400H may comprise an opening405 for receiving the fixture 507 (described above). The solid mold400G, 400H may be made from materials such as metal, composites, etc.which can withstand curing temperatures for the hollow preform 304C(illustrated in FIGS. 7B5, 7B6).

FIG. 7B2 is a cross-sectional view of the solid mold 400G, 400H of B1with a fixture 507 attached to a side 400G of the solid mold having anopening 405 according to an exemplary embodiment. The fixture 507illustrated in FIG. 7B2 is similar to the one illustrated in FIG. 7A.

FIG. 7B3 is a cross-sectional view of the solid mold 400G, 400H in whicha liquid state of preform material 304C is poured into the solid mold400G, 400H via the fixture 507 according to an exemplary embodiment. Thefixture 507 may receive a nozzle 503. The nozzle 503 may dispense theliquid state of the preform material 304C. The liquid state of thepreform material 304C may comprise a material similar to the embodimentdescribed in FIG. 7A. Specifically, the liquid state of the preformmaterial 304C may comprise equal parts of a diisocyanate such as soldunder the tradename FEATHERLITE Part A and a polyol such as FEATHERLITEPart B. The amount of diisocyante used generally comprises enough tocoat the mold and provide a uniform preform thickness of between about1.0 mm to about 10.0 mm.

FIG. 7B4 is a cross-sectional view of the solid mold 400G, 400Hcontaining the preform liquid material 304C while the solid mold 400G,400H is being rotated according to an exemplary embodiment.Specifically, after a requisite amount of liquid preform material 304Cis deposited in the solid mold 400G, 400H, the fixture 505 is sealed andthe solid mold 400G, 400H is rotated such that the preform material 304Ccures in attaches to the inner volume of the solid mold 400G, 400H inorder to generate a gas-impermeable, hollow type preform 304C. Thematerial described above for the preform 304C generally cures atstandard room temperature and pressure as understood by one of ordinaryskill in the art.

FIG. 7B5 is a cross-sectional view of the solid mold 400G, 400H beingopened after curing of the preform liquid material 304C into agas-impermeable, hollow preform 304C according to an exemplaryembodiment. The hollow preform 304C retains the fixture 507 aftercuring. The hollow preform 304C may have thickness which ranges betweenabout 1.0 mm and about 10.0 mm.

FIG. 7B6 is a cross-sectional view of the gas-impermeable, hollowpreform 304C after apertures or holes 701 have been created within thepreform according to an exemplary embodiment. Any number of holes 701may be created within the hollow preform 304C. The holes 701 may becreated with machines such as, but not limited to, drills or lasers. Theholes 701 may be randomly positioned or positioned at evenly spacedintervals as understood by one of ordinary skill in the art. The holes701 will help a fluid originating from the gaseous pressure source 403to exit the preform 304D in order to properly inflate the release layer302 as described above.

The outer surface of the hollow preform 304C may be sanded and finishedto the desired internal dimension that may be used for the self-sealingvolume 100 once formed, as understood by one of ordinary skill in theart. “Finished,” as described herein, means to sand and smooth so as toremove cracks, seams and imperfections as understood by one of ordinaryskill in the art.

FIG. 7C is a cross-sectional view of a device for forming flexible moldsaccording to another exemplary embodiment.

Referring now to FIG. 7C, this figure illustrates a cross-sectional viewof a device 400C, 400D for forming flexible molds 400E, 400F accordingto an exemplary embodiment. This figure is similar to FIG. 7A1 describedabove.

The device 400C, 400D may comprise two flexible molds shells that areused to create flexible molds 400E, 400F. The flexible mold shells 400C,400D may comprise a combination of convex and concave geometries. Forexample, see convex regions 802A, B and concave regions 804A, B.Additional and/or fewer convex regions 802A, B and concave regions 804A,B may be provided without departing from the scope of this disclosure.Further, these convex regions 802A,B and concave regions 804A,B may beadded to all molds described in this disclosure, such as thoseillustrated in FIG. 7B.

FIG. 8 is a flowchart 502A illustrating a routine or submethod 502A forgenerating the solid preform 304D of FIG. 7A according to an exemplaryembodiment. Block 702 is the first step of routine 502A. This routine502A corresponds with routine 502 described above in connection withFIG. 5A. As mentioned previously, routine 502 of FIG. 5A may have atleast two different paths or methods, such as illustrated in FIG. 8 andFIG. 9.

In block 702 of FIG. 8, a flexible, reusable mold 400E, 400F asillustrated in FIGS. 7A1-A3 is created. The flexible, reusable mold400E, 400F may be created with the use of supports or mold forms 400C,400D as set forth in FIG. 7A1. The flexible, reusable mold 400E, 400F,once created, may be used to generate a preform 304.

In block 704, the flexible, reusable mold 400E, 400F is removed fromsupports 400C, 400D as illustrated in FIG. 7A2. In block 706, a fixture507 may be positioned within an aperture 405 of a portion of theflexible, reusable mold 400E, 400F, such as in flexible mold 400F asillustrated in FIG. 7A3. The fixture 507 is positioned before thematerial for the preform 304B hardens.

In block 708, the material for the preform 304 is cast into theflexible, reusable mold 400E, 400F such as illustrated in FIG. 7A3. Inblock 710, the hardened preform materials forming preform sections 304A,304B may be removed from the flexible and reusable mold 400E, 400F asillustrated in FIG. 7A4. Next, in block 712, the preform sections 304A,304B may be fitted together and coupled permanently with the use ofadhesives as illustrated in FIG. 7A5.

In optional block 714, the outside of or external layer of the preform304D may be coated with a thermoset layer as illustrated in FIG. 7A5with the nozzle 707 dispersing a coating. Next, in block 716, thepreform 304D may be adjusted to precise dimensions that will correspondto the self-contained volume 100 described above. Specifically, in thisblock 716, adjusting may include sanding, buffing, cutting, shaving, andthe like, to the preform 304D. Subsequently, in block 716,apertures/holes 701 may be created within the solid, gas-permeablepreform 304D. The process then returns to block 505 of FIG. 5A.

FIG. 9 is a flowchart illustrating a routine or submethod for generatingthe hollow preform 304C of FIG. 7B according to an exemplary embodiment.Block 703 is the first step of routine 502B. This routine 502Bcorresponds with routine 502 described above in connection with FIG. 5A.As mentioned previously, routine 502 of FIG. 5A may have at least twodifferent paths or methods, such as illustrated in FIG. 8 and FIG. 9.

In block 703 of FIG. 9, the reusable mold 400G, 400H such as illustratedin FIG. 7B1 may be assembled/prepared. This reusable mold 400G, 400H mayproduce hollow preforms 304C as described above.

In block 705, a fixture 507 may be positioned within the reusable mold400G, 400H. Specifically, one section 400G of the reusable mold 400G,400H may have an aperture for receiving a fixture 507.

In block 707, preform material 304C may be poured in a liquid state froma nozzle 509 to the inside of the reusable mold 400G, 400H such asillustrated in FIG. 7B3. Next, in block 709, the reusable mold 400G,400H may be sealed and then rotated in three dimensions while the liquidpreform material 304C cures against the inside or internal wall of thereusable mold 400G, 400H.

In block 711, the hollow, gas-permeable preform 304C may be removed fromthe reusable mold 400G, 400H. The hollow gas-impermeable preform 304Cmay be adjusted to precise dimensions corresponding to theself-contained volume 100. Specifically, in this block 711, adjustingmay include sanding, buffing, cutting, shaving, and the like, to thepreform 304C. Subsequently, in block 713, apertures/holes 701 may becreated within the hollow, gas-impermeable preform 304D. The processthen returns to block 505 of FIG. 5A.

Elastomeric Material 102—Example 1

100 parts of a polyurethane dispersion such as Dispercoll U42 (which isan aqueous anionic dispersion of a high molecular weight polyurethane)having a solids content of 48-52%, a viscosity of 150-800 cps/mPa·s anda density of approximately 1.1 g/cm³ was spread onto a foam polyurethanepreform 304 that had been previously coated with a layer 302 of SmoothOn EZ Spray SILICONE® 20 silicone (which is a 20 Shore A siliconeelastomer) and a layer of inner liner 202 made from a polysulfide suchas PRC Rapid Seal 655 aliphatic polysulfide sold by PRC-DeSotoInternational, Inc.

Next about a 24 oz NYLON fabric 104B that had been previously coated anddried with a solvated polyurethane, namely Estane 5714, an aliphaticpolyurethane, or a polyether type thermoplastic polyurethane, was coatedwith the same polyurethane dispersion 102D and placed on the preform304, dispersion side down. This was followed by debulking under vacuumat 83° C. for 180 minutes.

The coating and drying of the nylon fabric 104B with Estane 5714 areoptional steps that can be dropped without departing from the scope ofthis disclosure. Samples of the preform were made for Example 1 withoutusing Estane 5714 or a solvated polyurethane. This dropping of the useof Estane 5714 (or any urethane) was also practiced for Examples 2 and 3described below.

Another layer of the same polyurethane dispersion 102C was placed on thepreform 304 and a layer of partially vulcanized natural rubber havingless than about 1% sulfur, forming the sealant layer 106. The sealantwas applied followed by adding another layer of the same polyurethanedispersion 102B to the sealant layer 106 and outer 24 oz NYLON fabric104A. This was followed by debulking under vacuum at 83° C. for 180minutes.

Next, the fuel tank was placed in one half of a three dimensional mold400. The second half 400A of the mold was closed onto the first half400B and the fuel tank 300A, 300B was heated for at least about 20.0minutes at a temperature of about 149° C. with no air pressure and thenheated for an additional 40 minutes at an air pressure of about 20 psifrom the gaseous pressure source 403 at a temperature of about 149° C.

Elastomeric Material 102—Example 2

100 parts of a polyurethane dispersion such as Dispercoll U42 (which isan aqueous anionic dispersion of a high molecular weight polyurethane)having a solids content of 48-52%, a viscosity of 150-800 cps/mPa·s anda density of approximately 1.1 g/cm³ was premixed with 5 parts of awater dispersible polyisocyanate such as Bayhydur 302 (which is a waterdispersible polyisocyanate based on hexmethylene diisocyanate).

This dispersion layer 102D was spread onto a foam polyurethane preform304 that had been previously coated with a layer 302 of Smooth On EZSpray SILICONE® 20 silicone (which is a 20 Shore A silicone elastomer)and a layer of inner liner 202 made from a polysulfide such as PRC RapidSeal 655 aliphatic polysulfide sold by PRC-DeSoto International, Inc.

Next about a 24 oz NYLON fabric 104B that had been previously coated anddried with a solvated polyurethane, namely Estane 5714, an aliphaticpolyurethane, or a polyether type thermoplastic polyurethane (as notedpreviously, coating and drying with a urethane is an optional step), wascoated with the same polyurethane dispersion 102D and placed on thepreform 304, dispersion side down. This was followed by debulking undervacuum at 83° C. for 180 minutes.

Another layer of the same polyurethane dispersion 102C was placed on thepreform 304 and a layer of partially vulcanized natural rubber havingless than about 1% sulfur, forming the sealant layer 106. The sealantwas applied followed by adding another layer of the same polyurethanedispersion 102B to the sealant layer 106 and outer 24 oz NYLON fabric104A. This was followed by debulking under vacuum at 83° C. for 180minutes.

Next, the preform was placed in one half of a three dimensional mold400. The second half 400A of the mold was closed onto the first half400B and the fuel tank 300A, 300B was heated for at least about 20.0minutes at a temperature of about 149° C. with no air pressure and thenheated for an additional 40 minutes at an air pressure of about 20 psifrom the gaseous pressure source 403 at a temperature of about 149° C.

Elastomeric Material 102—Example 3

100 parts of a polyurethane dispersion such as Dispercoll U42 (which isan aqueous anionic dispersion of a high molecular weight polyurethane)having a solids content of 48-52%, a viscosity of 150-800 cps/mPa·s anda density of approximately 1.1 g/cm³ was premixed with 5 parts of awater dispersible polyisocyanate such as Bayhydur 302 (which is a waterdispersible polyisocyanate based on hexmethylene diisocyanate). This wasapplied to all 24 oz Nylon fabric 104 used in wall structure 100 thathad been previously coated and dried with a solvated polyurethane,namely Estane 5714, an aliphatic polyurethane, or a polyether typethermoplastic polyurethane (but as noted previously, coating and dryingwith a urethane is an optional step). The polyurethane dispersion wascured for 60 minutes at 100° C.

100 parts of a polyurethane dispersion such as Dispercoll U42 (which isan aqueous anionic dispersion of a high molecular weight polyurethane)having a solids content of 48-52%, a viscosity of 150-800 cps/mPa·s anda density of approximately 1.1 g/cm³ was spread onto a foam polyurethanepreform 304 that had been previously coated with a layer 302 of SmoothOn EZ Spray SILICONE® 20 silicone (which is a 20 Shore A siliconeelastomer) and a layer of inner liner 202 made from a polysulfide suchas PRC Rapid Seal 655 aliphatic polysulfide sold by PRC-DeSotoInternational, Inc.

Next about a 24 oz NYLON fabric 104B was coated with the samepolyurethane dispersion 102D and placed on the preform 304, dispersionside down. This was followed by debulking under vacuum at 83° C. for 180minutes.

Another layer of the same polyurethane dispersion 102C was placed on thepreform 304 and a layer of partially vulcanized natural rubber havingless than about 1% sulfur, forming the sealant layer 106. The sealantwas applied followed by adding another layer of the same polyurethanedispersion 102B to the sealant layer 106 and outer 24 oz NYLON fabric104A. This was followed by debulking under vacuum at 83° C. for 180minutes.

Next, the fuel tank was placed in one half of a three dimensional mold400. The second half 400A of the mold was closed onto the first half400B and the fuel tank 300A, 300B was heated for at least about 20.0minutes at a temperature of about 149° C. with no air pressure and thenheated for an additional 40 minutes at an air pressure of about 20 psifrom the gaseous pressure source 403 at a temperature of about 149° C.

Certain steps in the processes or process flows described in thisspecification naturally precede others for the invention to function asdescribed. However, the invention is not limited to the order of thesteps described if such order or sequence does not alter thefunctionality of the invention. That is, it is recognized that somesteps may preformed before, after, or parallel (substantiallysimultaneously with) other steps without departing from the scope andspirit of the invention.

For example, in an alternative exemplary embodiment, the urethanedispersion 102 may be applied according to the following sequence: tothe inner liner 202, similar to step 525; then, the elastomeric material102 may be applied to the fabric layer 104; then the fabric layer 104may then be applied to the inner liner 202, similar to step 525; thenthe elastomeric material 102 may be applied to the fabric layer 104again; then, the sealant layer 106 may be applied, similar to step 545;and then, the polyurethane dispersion 102 may be applied to a secondfabric layer 104.

In some instances, certain steps may be omitted or not preformed withoutdeparting from the invention. Further, words such as “thereafter”,“then”, “next”, etc. are not intended to limit the order of the steps.These words are simply used to guide the reader through the descriptionof the exemplary method.

As noted previously, at least one inventive aspect of the inventivesystem and method is that the preform 304 is inflated during cure of theelastomeric material included in layer 100. With this inflation of thepreform 304, the wall system 200 conforms to the exact dimensions of themold 400 which holds the preform 304 and the wall system 200 sandwichedthere between. This process yields a dimensionally correct/preciselybuilt self-sealing volume 200.

According to an additional exemplary embodiment, a first barrier layer(not illustrated) may be provided between the liner 202 and the sealant106. The purpose of the barrier layer is to limit the permeation of fuel204 over time through the inner liner layer 202, the elastomericmaterial layer 102D, the fabric layer 104B, and the elastomeric materiallayer 102C. A second barrier layer, like the first barrier layer (bothnot illustrated) may also be provided on the exterior of theself-sealing volume 200 to also limit fuel permeation from fuel 204 thatmay come in contact with the volume 200, such as through a spill or leakfrom another volume or source.

Although selected aspects have been illustrated and described in detail,it will be understood that various substitutions and alterations may bemade therein without departing from the spirit and scope of the presentinvention, as defined by the following claims.

What is claimed is:
 1. A method for making a self-sealing volume, themethod comprising: coating an inflatable preform with a material forforming the self-sealing volume and for forming one or more passagesthat allow for the escape of a fluid, the material comprising anelastomeric material dispersed or dissolved in a liquid medium; placingthe preform having the material into a mold; inflating the materialagainst the mold with the fluid; allowing the fluid to escape throughthe one or more passages; and curing the material with the mold to formthe self-sealing volume.
 2. The method of claim 1, wherein theelastomeric material comprises at least one of polyurethanes, polyureas,polyurethane ureas, epoxy, polyester, and silicones.
 3. The method ofclaim 1, wherein the elastomeric material comprises a polyurethanedispersion layer.
 4. The method of claim 3, wherein the polyurethanedispersion layer comprise an aqueous anionic dispersion of polyurethanewith a molecular weight of at least about 335,000.00.
 5. The method ofclaim 1, wherein the material comprises fabrics made from at least oneof nylon, polyester, polypropylene, polyethylene and an aramid.
 6. Themethod of claim 1, wherein the material comprises at least one of asealant calendared onto a fabric and a sealant calendared between twolayers of fabric.
 7. The method of claim 1, wherein the one or morepassages are positioned in at least one of a corner of the self-sealingvolume, and a side of the self-sealing volume.